Cubical blocks of mass m and side l are piled up in a vertical column.The total gravitational potential energy of a column of three blocks is
A) $\frac { 5 } { 2 }$ mgl.
B)3mgl.
C) $\frac { 9 } { 2 }$ mgl.
D)6mgl.
E)9mgl.

Question

Quizplus · Accepted Answer

The gravitational potential energy of a single block of mass m and side l at a height h is given by U = mgh.

For the bottom block in the column, the height is 0, so U = 0. 
For the middle block, the height is l, so U = mgl. 
For the top block, the height is 2l, so U = 2mgl.

Adding these together, we get the total gravitational potential energy of the column:

U_total = 0 + mgl + 2mgl = 3mgl

Therefore, the correct answer is (C) 11ea99f6_d748_fa78_8bb6_2537e1ea7d27_TB5764_11_TB5764_11_TB5764_11_TB5764_11_TB5764_11_TB5764_11_TB5764_11_TB5764_11 mgl.

Cubical Blocks of Mass M and Side L Are Piled 52\frac { 5 } { 2 }25​

Cubical Blocks of Mass M and Side L Are Piled $\frac { 5 } { 2 }$